The overall objective of the proposed research is to study the neural basis for hearing, using neuroanatomical and behavioral methods. It is proposed to examine in detail the connections of ascending Auditory pathways in the brain stem of mammals. Pathways ascending from the cochlear nucleus and superior olivary complex will be examined. Particular emphasis will be placed on how these pathways converge and diverge from one another as they terminate in the inferior colliculus. It is expected that the anatomical results will provide hypotheses about function of auditory pathways in the brain stem. These hypotheses will be tested in behavioral experiments of auditory discriminations before and after ablation of auditory centers of the brain. Methods to show neural connections include techniques for retrograde axonal transport of horesradish peroxidase and anterograde transport of tritiated amino acids.